Maria Bukowska

MODIFICATION OF THE PROPERTIES OF CONCRETE BY A NEW POZZOLAN- A WASTE CATALYST FROM THE CATALYTIC PROCESS IN A FLUIDIZED BED

Abstract The zeolitic waste material studied (fluidized bed cracking catalyst, FBCC) is characterised by a content of more than 90 wt.% of SiO 2 and Al 2 O 3 , a mean grain size within 20–80 μm, and a specific surface above 100 m 2 /g. Its chemical composition makes it similar to some fly ashes and metakaolin. The present work was devoted to the study of the mechanism of interaction of FBCC with Portland cement and of the pozzolanic activity. Concretes were made with FBCC additions of 10% and 20% (relative to the mass of cement) used as a substitute for the sand aggregate fraction, and the following properties of the concretes were determined under nonaggressive conditions: compressive strength, porosity, water absorption, frost resistance, and steel passivation ability. It has been found that FBCC has pozzolanic properties, and its pozzolanic activity depends on its grain size. FBCC favourably modifies the porous structure of the concretes, increases their compressive strength, density, and frost resistance, and reduces water absorption. The effectiveness of FBCC increases under conditions of strong dispersion. FBCC does not deteriorate the steel passivation ability of concrete when used as a 10% additive, but at a content of 20 wt.%, it can make difficult the formation of a passive layer that conforms to the Polish standards.

Effect of waste aluminosilicate material on cement hydration and properties of cement mortars

Abstract The effect of waste material (catalyst used previously in catalytic cracking of petroleum in fluidized bed—fluidized bed cracking catalyst denoted as FBCC) on cement hydration kinetics was investigated in terms of fineness of this admixture. The compressive strength and microstructure of cement mortars were also examined. Variable percentage of this aluminosilicate admixture, originating from batches of quite different grain size composition, was introduced to cement pastes. Further on, cement mortars were produced using the material of higher activity, as it has been found in admixtured cement investigations. The waste was added as cement replacement or, partially, as sand replacement. The activity of waste catalyst was strongly related to the fineness—finer grains indicate better activity. In the presence of a FBCC admixture, the Ca(OH)2 content decrease in cement pastes due to the pozzolanic reaction is observed. The surface area of hydrated paste becomes higher and, simultaneously, the mean pore diameter decreases, as compared to reference sample, without admixture. The strength improvement is observed particularly when the aluminosilicate material is introduced as partial sand replacement.

Hydration of Cement Slurry in The Presence of Spent Cracking Catalyst

The physicochemical properties of spent fluidized bed cracking catalyst and its influence on hydration process of cement slurry were studied. The samples were cement slurries prepared with water/solid=0.5 and additions of used catalyst amounted to 0, 5, 10, 15, 20 and 25%with resp. to the solid. After definite time they were subjected to thermogravimetric analysis (TG, DTG, DTA) and, in order to determine the progress of reaction with water, the heat of hydration was measured by means of isotherm calorimetry. The studies disclosed that the spent cracking catalyst is not merely an inactive filler in cement slurries, but it modifies the course of the hydration process. The spent catalyst is a pozzolana additive and its presence leads to a decrease of calcium hydroxide contents in the system. The spent catalyst affect on the heat of cement hydration. Small amounts additive accelerate the process of binding.

INFLUENCE OF SOME AGGRESSIVE MEDIA ON CORROSION RESISTANCE OF MORTARS WITH SPENT CRACKING CATALYST

The influence of spent catalyst from catalytic cracking in fluidized bed on the hydration process of cement and the properties of cement mortars were studied. The spent catalyst was used as an additive to cement in the mortars (10 and 20% of cement). The samples of mortars kept in water for28 days, then they were placed in sulfate and chloride media for 2 months (the control samples were kept in water for 3 months). After this time they were subjected to bending strength and compressive strength determinations. Thermogravimetric and infrared absorption studies were performed and capillary elevation, capability of binding heavy metals, and changes in mass and apparent density were determined too. The studies disclosed the pozzolana nature of spent catalyst and its influence on cement mortars being in contact with corrosive media.

Trimethylsilylation of cyclodextrins with N-(trimethylsilyl)acetamide in N,N-dimethylformamide

Abstract Trimethylsilylation of α- and β-cyclodextrin with N-(trimethylsilyl)acetamide in N,N-dimethylformamide gives the per-2,6-O-trimethylsilyl derivatives with high yield and selectivity.

An imidazopyrazine-derived anion for lithium conducting electrolyte application

In this work we present a new lithium salt of 4,5-dicyano-2-(trifluoromethyl)imidazopyrazine (LiTDPI) which was designed for use as an electrolyte in lithium-ion cells. It was synthesized and completely characterized by NMR techniques. The salt is thermally stable up to 350 °C and electrochemically stable in carbonate solvents up to +5.1 V vs. Li. Basic electrochemical characterization of this new lithium salt solution shows conductivity of over 2 mS cm−1 at room temperature and a transference number which is higher than the commercial reference salt, LiPF6 (>0.4 in a EC:DMC 1:2 ratio mixture). As a proof of concept, short cycling measurements in a graphite half-cell show good capacity (352 mA h g−1) and capacity retention (96% after 50 cycles). The extremely good stability without compromising the performance parameters shows the next leap in progress for tailoring efficient lithium-conducting electrolytes.